The Molecular Membrane Biology (MMB) Program provides a long-standing forum for AECC investigators with a primary interest in determining roles in cancer for molecules that function at the cell surface or in the secretory pathway of mammalian cells. The goals are to determine structure/function relationships of molecules that reside in cell membranes or enveloped viruses, and to exploit their properties in cancer diagnosis, prognosis or treatment. In the past 5 years program members have identified new mechanisms of tumorigenesis, tumor progression, angiogenesis and metastasis and mechanisms of resistance to chemotherapeutic drugs. The group now comprises 18 members, including 4 new primary and one new secondary member, from 11 departments. Secondary appointees are from the Departments of Medicine, Pediatrics and Oncology. Sadly two members unexpectedly passed away in the last year. Another member was not renewed by AECC and one member moved to another cancer center. In the last budget year, MMB members were supported by 10 NCI grants ($2.4M direct), a Susan Komen award, and an additional 15 NIH grants. About a third of the MMB group investigates membrane transporters, including the Na+/l- symporter (NIS), glucose transporters (GLUT4 and GLUTS), folate transporters, the F1/FO ATP synthase, a multi-drug resistance transporter, prostaglandin transporters and the Na+/monocarboxylate transporter (SMCT). Several members investigate mechanisms of membrane trafficking and secretion including two virologists investigating mechanisms of virus assembly and membrane fusion in viruses that either cause cancer, or belong to a family of viruses that cause cancer. Another focus is on cell surface interactions mediated by Nglycans, Notch receptors, cadherins, and galectins. The group published 189 cancer relevant papers in the last 5 years; 12% represented intraprogrammatic, and 29% interprogrammatic, collaborations. Future goals for the MMB program are to catalyze discoveries of new roles for membrane molecules in cancer diagnosis, prognosis and treatment to clinical applications, to expand the program to include scientists investigating integrins and selectins in cancer through new recruitment, and to enhance interactions with the Tumor Microenvironment and Metastasis group in order to expand the scope of cancer research in cell-cell interactions and membrane-related phenomena.